Fluorescence Detection of Deoxyadenosine in spp. by Indicator Displacement Assay.

A rapid, sensitive and reliable indicator displacement assay (IDA) for specific detection of 2'- and 3'-deoxyadenosine (2'-dAde and 3'-dAde), the latter is also known as cordycepin, was established. The formation of inclusion complex between protonated acridine orange (AOH) and cucurbit[7]uril (CB7) resulted in the hypochromic shift of fluorescent emission from 530 nm to 512 nm. Addition of cordycepin to the highly fluorescent AOH/CB7 complex resulted in a unique tripartite AOH/CB7/dAde complex with diminished fluorescence, and such reduction in emission intensity serves as the basis for our novel sensing system. The detection limits were 11 and 82 μM for 2'- and 3'-deoxyadenosine, respectively. The proposed method also demonstrated high selectivity toward 2'- and 3'-deoxyadenosine, owing to the inability of other deoxynucleosides, nucleosides and nucleotides commonly found in spp. to displace the AOH from the AOH/CB7 complex, which was confirmed by isothermal titration calorimetry (ITC), UV-Visible and proton nuclear magnetic resonance (H-NMR) spectroscopy. Our method was successfully implemented in the analysis of cordycepin in commercially available and supplements, providing a novel and effective tool for quality assessment of these precious fungi with several health benefits.